E-cigarettes were nearly twice as effective as nicotine patches, gums and similar therapies in helping people stop smoking cigarettes, a study published Wednesday in the New England Journal of Medicine found.

United Kingdom, which has embraced and even encouraged e-cigarettes as an alternative for adult smokers.

In an editorial accompanying the study, professors from the Boston University School of Medicine urged doctors to use caution when recommending e-cigarettes for smoking cessation. They said doctors should only recommend e-cigarettes when an FDA-approved treatment fails, and that if doctors do suggest e-cigarettes, they should manage their use like they would with other products.

“While e-cigarettes are ‘safer’ than traditional cigarettes, they are not without risks,” Boston University professors Belinda Borrelli and George O’Connor said in a statement.

They also pointed to the finding that at the one-year mark, 80 percent of people in the e-cigarette group were still using the devices. So while people stopped smoking cigarettes, they were still using e-cigarettes. The study’s authors also noted this finding, saying it “can be seen as problematic if e-cigarette use for a year signals ongoing long-term use, which may pose as-yet unknown health risks.”

Huge numbers of teens using the products — particularly one brand, Juul — have soured perceptions about e-cigarettes in the U.S. Even Food and Drug Administration Commissioner Scott Gottlieb, who has championed the devices as a way to help adult smokers, says the industry is at a tipping point.

Ray Niaura, a professor of social and behavioral sciences at New York University, said the study’s results are “encouraging.” They also suggest researchers can find ways to keep more people cigarette-free longer, said Niaura, who was not involved in the study.

At the six-month mark, 35 percent of people in the e-cigarette group were still cigarette-free. That dropped to 18 percent at the one-year mark.